Hopper truck trailers are in common use for towing by truck tractors to transport bulk material such as grain, gravel, coal, salt, fertilizer, and the like. The bulk material is typically loaded into an open top of the trailer into hoppers formed in the trailer and unloaded via chutes provided beneath. Tarps or other flexible sheet materials are typically used to cover the open top during transport.
Partial cross-sectional views of a known hopper trailer 100 are shown in FIGS. 1 to 3. The known hopper trailer 100 has a container, or box, with opposing sidewalls 101 and end walls (not shown). The opposing sidewalls 101 are supported by a floor frame 103 including transverse cross members 104 (shown especially in FIG. 2, only one of six cross members 104 identified by a lead line for clarity of illustration). The conventional hopper trailer further has hopper slopes 105 which internally span the sidewalls 101 to form hoppers 102, with a bottom opening 106 and a gate or door (not shown) for selectively opening a bottom chute 107 of the hopper for emptying the hopper through the chute 107 by gravity. Upper cross beams 108 are also typically provided which span and join the sidewalls 101 and support the hopper slopes 105 at an upper end thereof. The known hopper trailer 100 is typically mounted on and carried by a trailer chassis 109 which is in turn mounted on a wheeled suspension 110.
As shown in FIG. 3, the known hopper trailer 100 construction results in an indirect transmission of the weight of a load contained in the hopper to the ground. The weight first bears on the hopper slopes 105 and transfers to the upper cross beams along arrow 111, which it then traverses to the sidewalls along arrow 112, then down the sidewalls along arrow 113, then back across the floor frame cross-members along arrow 114, down through the chassis and suspension along arrow 115, transversely along the axle to the wheel along arrow 116, and finally down to the road or other supporting surface beneath along arrow 117.
The indirect weight transmission typically results in bending stresses at least in the hopper slopes and floor frame, which must therefore be constructed of materials of sufficient strength, and in sufficient dimensions, to resist bending. In particular, in order to redirect the weight from the sidewalls 101 to the chassis 109, it is typically necessary to provide the floor frame 103 with I-beam cross-members 104, which adds to the construction cost and weight of the trailer, as well as its height. Not only does this increase initial manufacturing costs, but it increases the cost of hopper load transport which is dependent at least in part on the weight of the transport vehicle including the weight of the hopper trailer.
It is desirable, therefore, to improve the design of hopper trailers in order to enable a less costly and more efficient solution.
Where appropriate, like reference characters designate like elements throughout the drawings.